protected SqlQueryableProvider(DbConnection connection, SqlQueryVisitor visitor)
{
if (connection == null)
{
throw new ArgumentNullException(nameof(connection));
}
if (visitor == null)
{
throw new ArgumentNullException(nameof(visitor));
}
this.connection = connection;
this.visitor = visitor;
}
public static IEnumerable <Record> ExecuteQuery(this DbConnection connection, ASourceExpression expression, SqlQueryVisitor visitor)
{
// Create the outer select expression
SelectExpression select = expression as SelectExpression;
if (select == null)
{
select = new SelectExpression(expression, expression.Fields);
}
// Ensure the connection is open
if (connection.State != ConnectionState.Open)
{
throw new InvalidOperationException("The connection must be open to execute a query.");
}
// Create the command
LinkedList <Record> items = new LinkedList <Record>();
using (DbCommand command = connection.CreateCommand())
{
// Prepare the query
Query query = visitor.GenerateQuery(select);
command.CommandText = query.Sql;
foreach (KeyValuePair <string, object> pair in query.Parameters)
{
command.AddParameter(pair.Key, pair.Value);
}
// Execute the query
using (DbDataReader reader = command.ExecuteReader())
{
ILookup <string, CommandField> fields = reader.GetFieldMap(select.Fields);
while (reader.Read())
{
// Read the row of the result set
Dictionary <string, RecordItem> row = fields
.Select(x => ReadItem(reader, x, x.Key))
.ToDictionary(x => x.Key);
// At this point the row has been created
items.AddLast(new Record(row));
}
}
}
return(items);
}
